There is no water in your lungs the reason the gas kills is because it depletes(pushes) aside the air containing oxygen.
If you had water in your lungs it would either be because you had drowned or were dead.
Either way cholrine gas is nasty, but it does not turn to acid, in contact with water it is an acidic compounsd in itself.
The reason for peeing on a rag and covering face was merely so the rag was wet, water or any liquid would have made a better filter than a rag on it's own, to keep out the gas which is a GREENISH YELLOWY liquid.
There are much more nasty liquids around though and can be made in your own kitchen!!, and simply and cheaply, if you can make toast you could make these!!.
tabetha